Exoplanets – worlds of other suns

weatheriscool
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Re: Exoplanets – worlds of other suns

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TESS discovery of a super-Earth and two sub-Neptunes orbiting the bright, nearby, Sun-like star HD 22946
https://arxiv.org/abs/2209.09597
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HD 23472: A multi-planetary system with three super-Earths and two potential super-Mercuries
https://arxiv.org/abs/2209.13345
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caltrek
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Newly Discovered ‘Super-Earth’ Planet May Be Able to Support Life
by Madeleine Muzdakis
September 27, 2022

Extract:
(MY Modern Met) The University of Liège researchers…through their advanced telescope nicknamed SPECULOOS (Search for habitable Planets EClipsing ULtra-cOOl Stars)…spotted (a super-Earth planet).. known as LP 890-9b, is 30% larger than Earth and orbits its own sun in 2.7 days. (A)… second (planet) was dubbed LP 890-9c (or SPECULOOS-2c). It is 40% larger than Earth with an orbit of 8.5 days.

Francisco Pozuelos, of the Institute of Astrophysics of Andalusia and co-author of a recent paper on the planets, indicated in a statement that SPECULOOS-2c could potentially sustain life. While it is only 3.7 million miles from its sun—versus Earth's 93 million mile distance—the planet's environment may be able to maintain liquid water. “Although this planet orbits very close to its star, at a distance about 10 times shorter than that of Mercury around our Sun, the amount of stellar irradiation it receives is still low, and could allow the presence of liquid water on the planet's surface, provided it has a sufficient atmosphere,” Pozuelos says.

“This is because the star LP 890-9 [the exoplanet's sun] is about 6.5 times smaller than the Sun and has a surface temperature half that of our star.” While it may be presently unclear whether life exists on the super-Earth, the find itself is exciting.
Read more here: https://mymodernmet.com/super-earth-speculoos/
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Re: Exoplanets – worlds of other suns

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Discovery Alert: A Rocky 'Super-Earth' in the Habitable Zone
https://exoplanets.nasa.gov/news/1712/d ... PVwk8gpye4
By Pat Brennan, NASA's Exoplanet Exploration Program
The discovery: LP 890-9 c, a “super-Earth” in the habitable zone of its star.

Key facts: The planet, likely rocky but 40% larger than Earth, came to light during follow-up observations of its sister planet, LP 890-9 b. Both fall into the super-Earth category – exoplanets, or planets around other stars, that are up to 75% larger than our own but believed to be rocky worlds, like Earth. Surface conditions might or might not be similar.
The latest

Details: Both planets orbit a comparatively cool, red-dwarf star, LP 890-9, about 98 light-years away. The inner planet, discovered using the Transiting Exoplanet Survey Satellite (TESS), is about 30% larger than Earth and, with an estimated temperature of 253 degrees Fahrenheit (123 Celsius), probably too hot to be habitable. The outer planet, though possibly chilly by human standards at an estimated 30 Fahrenheit (minus 1.1 Celsius), sits within its star’s habitable zone, the orbital distance where liquid water might be present on the surface. This planet was detected using a ground-based telescope survey, the Search for habitable Planets EClipsing Ultra-cOOl Stars (SPECULOOS). The observations not only met their original goal – confirming the existence of the innermost planet – but unexpectedly discovered a second planet in the system.
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Heaviest Element Yet Detected In Exoplanet Atmospheres Where It Rains Iron And Jewels
by Dr Alfredo Carpineti
October 14, 2022

Introduction:
(IFL Science) Astronomers have discovered something puzzling in the atmospheres of two exoplanets: barium. The 56th member of the periodic table is the heaviest element ever discovered in the atmosphere of an exoplanet, detected in the upper layers of two peculiar worlds, both ultra-hot Jupiters: WASP-76 b and WASP-121 b. And we're not exaggerating when we say peculiar. Scientists think it rains iron on WASP-76b, and liquid sapphires and rubies might be falling on the night side of WASP-121b.

These gas giant exoplanets orbit extremely close to their stars, much closer than Mercury is to the Sun. They reach incredible temperatures of over 1,000°C (1800°F), hot enough to melt and vaporize metals, including barium. Although it's unclear how the barium got so high up, given that it is 2.5 times heavier than iron.

“The puzzling and counterintuitive part is: why is there such a heavy element in the upper layers of the atmosphere of these planets?” lead author Tomás Azevedo Silva, of the University of Porto and the Institute of Astrophysics and Space Sciences in Portugal, said in a statement.

“Given the high gravity of the planets, we would expect heavy elements like barium to quickly fall into the lower layers of the atmosphere,” added co-author Olivier Demangeon, a researcher in the same institutions.

The presence of barium and the question of how it was transported to the upper atmosphere suggests that we might understand less about these planets’ atmospheres than we previously thought. Ultra-hot Jupiters are inflated due to their high temperatures which are extremely advantageous to study their atmospheres.
Read more here: https://www.iflscience.com/heaviest-el ... els-65762
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Re: Exoplanets – worlds of other suns

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Three Red Suns in the Sky: A Transiting, Terrestrial Planet in a Triple M Dwarf System at 6.9 Parsecs
https://arxiv.org/abs/1906.10147
We present the discovery from TESS data of LTT 1445Ab. At a distance of 6.9 parsecs, it is the second nearest transiting exoplanet system found to date, and the closest one known for which the primary is an M dwarf. The host stellar system consists of three mid-to-late M dwarfs in a hierarchical configuration, which are blended in one TESS pixel. We use follow-up observations from MEarth and the centroid offset analysis in the TESS data validation report to determine that the planet transits the primary star in the system. The planet has a radius 1.35 R_Earth, an orbital period of 5.35882 days, and an equilibrium temperature of 428 K. With radial velocities from HARPS, we place a three-sigma upper mass limit of 8.4 M_Earth on the candidate. The planet provides one of the best opportunities to date for the spectroscopic study of the atmosphere of a terrestrial world. The presence of stellar companions of similar spectral type may facilitate such ground-based studies by providing a calibration source to remove telluric variations. In addition, we present a detailed characterization of the host stellar system. We use high-resolution spectroscopy and imaging to rule out the presence of any other close stellar or brown dwarf companions. Nineteen years of photometric monitoring of A and BC indicates a moderate amount of variability, in agreement with the observed low-level, short-term variability in the TESS light curve data. We derive a preliminary astrometric orbit for the BC pair that reveals an edge-on and eccentric configuration. The presence of a transiting planet in this system raises the possibility that the entire system is co-planar, which implies that the system may have formed from the early fragmentation of an individual protostellar core.
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Re: Exoplanets – worlds of other suns

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weatheriscool wrote: Wed Oct 19, 2022 6:14 pm Three Red Suns in the Sky: A Transiting, Terrestrial Planet in a Triple M Dwarf System at 6.9 Parsecs
https://arxiv.org/abs/1906.10147
We present the discovery from TESS data of LTT 1445Ab. At a distance of 6.9 parsecs, it is the second nearest transiting exoplanet system found to date, and the closest one known for which the primary is an M dwarf. The host stellar system consists of three mid-to-late M dwarfs in a hierarchical configuration, which are blended in one TESS pixel. We use follow-up observations from MEarth and the centroid offset analysis in the TESS data validation report to determine that the planet transits the primary star in the system. The planet has a radius 1.35 R_Earth, an orbital period of 5.35882 days, and an equilibrium temperature of 428 K. With radial velocities from HARPS, we place a three-sigma upper mass limit of 8.4 M_Earth on the candidate. The planet provides one of the best opportunities to date for the spectroscopic study of the atmosphere of a terrestrial world. The presence of stellar companions of similar spectral type may facilitate such ground-based studies by providing a calibration source to remove telluric variations. In addition, we present a detailed characterization of the host stellar system. We use high-resolution spectroscopy and imaging to rule out the presence of any other close stellar or brown dwarf companions. Nineteen years of photometric monitoring of A and BC indicates a moderate amount of variability, in agreement with the observed low-level, short-term variability in the TESS light curve data. We derive a preliminary astrometric orbit for the BC pair that reveals an edge-on and eccentric configuration. The presence of a transiting planet in this system raises the possibility that the entire system is co-planar, which implies that the system may have formed from the early fragmentation of an individual protostellar core.
This isn't new, though. Published June 2019.
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Re: Exoplanets – worlds of other suns

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Gas Giant Planet With Density of a Marshmallow Breaks All The Rules
by Stephen Luntz
October 21, 2022

Introduction:
(IFL Science) Patterns have emerged in the thousands of planets recently discovered orbiting stars besides the Sun. So when planets are found that break those patterns, astronomers get curious, particularly when they have been confident in their explanations for what they have seen.

The latest rule-breaker goes by the not-exactly rebellious-sounding name of TOI-3757 b and lies 580 light-years away in the constellation Auriga. Its radius is 10 percent greater than Jupiter’s, but its mass is barely a quarter as great. In fact, it's the lowest-density gas giant ever found orbiting a red dwarf.

Saturn famously has a density lower than water, leading to children’s astronomy books sometimes picturing It floating on an immense ocean. TOI-3757 b is 60 percent less dense still; just 0.27 grams per cubic centimeter (0.037 pounds per cubic foot). The astronomers who found it have compared it to a marshmallow, so perhaps we need a giant hot chocolate in which it can bob.

Light as it is, if TOI-3757 b was orbiting a more Sun-like star it wouldn’t stand out. However, gas giants are rare around red dwarfs to start off with – just 10 have been found, 0.2 percent of known planets, so one so insubstantial requires explanation.

One clue to TOI-3757 b’s likely formation lies in the fact its parent star, TOI-3757, has the lowest metal abundance (astronomically defined as anything heavier than helium) of the red dwarfs known to have giant planets. The composition of the disk from which planets form reflects that of the star, so it’s likely heavier elements were in short supply when TOI-3757 b formed.
Read more here: https://www.iflscience.com/gas-giant-p ... les-65879
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A Nearby Star Has Completely Blasted Away the Atmosphere From its Planet
by Carolyn Collins Petersen
October 22, 2022

Introduction:
(Universe Today) What if you placed an Earth-sized planet in a close orbit around an M-dwarf star? It’s more than an academic question since M dwarfs are the most numerous stars we know. A group of astronomers studying the planet GJ 1252b found an answer and it’s not pretty.

Since this planet is so close to its star, it receives a lot of heat. And that proximity is deadly in another way. “The pressure from the star’s radiation is immense, enough to blow a planet’s atmosphere away,” said Michelle Hill, a University of California Riverside astrophysicist and co-author of a recent paper focused on GJ 1252b. The planet lies some 65 light-years from Earth and orbits its star twice every 24 Earth hours. The heat from the star renders this world inhospitable.

This is not terribly different from Mercury in our solar system. There’s no atmosphere and the planet is alternately heated and frozen as it orbits the Sun. In fact, Earth also loses a little atmosphere to solar activity. However, volcanism and other processes release gases back into our atmosphere. Earth is lucky; planets like Mercury and GJ 1252b are not. And, that has profound implications in the search for life-friendly worlds.
Read more here: https://www.universetoday.com/158217/a ... re-158217


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Illustration of the atmosphere being blown away from a planet by a nearby star.
NASA
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Ways JWST Could Detect Alien Life
by Matt Williams
October 27, 2022

Introduction:
(Universe Today) Less than a year after it went to space, the James Webb Space Telescope (JWST) has already demonstrated its worth many times over. The images it has acquired of distant galaxies, nebulae, exoplanet atmospheres, and deep fields are the most detailed and sensitive ever taken. And yet, one of the most exciting aspects of its mission is just getting started: the search for evidence of life beyond Earth. This will consist of Webb using its powerful infrared instruments to look for chemical signatures associated with life and biological processes (aka. biosignatures).

The chemical signatures vary, each representing a different pathway toward the potential discovery of life. According to The Conversation’s Joanna Barstow, a planetary scientist and an Ernest Rutherford Fellow at The Open University specializing in the study of exoplanet atmospheres, there are four ways that Webb could do this. These include looking for chemicals that lifeforms depend on, chemical byproducts produced by living organisms, chemicals essential to maintaining a stable climate, and chemicals that shouldn’t coexist.

In their search for life beyond Earth, astrobiologists have been restricted to the “low-hanging fruit” approach. This consists of searching for terrestrial (or rocky) planets that orbit within their parent stars’ circumsolar habitable zones (HZs) or the distance where planets will be warm enough to maintain liquid water on their surfaces. With next-generation telescopes like Webb, which combine sensitive optics, coronographs, and spectrometers with near- and mid-infrared imaging capability, the field of exoplanet study is transitioning from discovery to characterization.

As we explored in previous articles, this involves direct imaging studies of exoplanets and obtaining spectroscopic data from their atmospheres. Since the early 19th century, scientists have known that certain chemical elements absorb light at certain wavelengths and radiate it in others. By performing a “chemical inventory” of exoplanet atmospheres, astrobiologists will be able to place much tighter constraints on exoplanet habitability. In other words, they will be able to say with much greater confidence if a planet is habitable (and not just “potentially habitable”).
Read more here: https://www.universetoday.com/158228/h ... re-158228
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